Carbonaceous substrates, and more specifically carbon-carbon composites are widely used in the aerospace and aviation industries due to the physical and mechanical properties of such materials. The high strength-to-weight ratio of carbon-carbon composites provides weight savings to aircraft components. This characteristic, coupled with the mechanical strength, toughness and dimensional stability of carbon-carbon composites to temperatures in excess of 4000.degree. F. makes these materials ideal for aerospace applications.
A potentially limiting characteristic of carbon-carbon composites is that such materials tend to rapidly oxidize at temperatures above 800.degree. F. in oxygen-containing environments. The degradation of the material due to oxidation causes loss of mechanical and physical properties. This problem must be prevented in order for these materials to be effectively used for aerospace applications, such as turbine engine exhaust nozzles the invention that follows, and in the examples and claims appended hereto.